Acoustic wave resonator, filter, multiplexer, and wafer

Abstract

An acoustic wave resonator includes a support substrate, a piezoelectric layer that is disposed on the support substrate and is a rotated Y-cut X-propagation lithium tantalate of which a cut angle is within a range of greater than 50° and less than 150°, and a pair of comb-shaped electrodes disposed on the piezoelectric layer, each of the comb-shaped electrodes including a plurality of electrode fingers, an average pitch of the electrode fingers of one of the comb-shaped electrodes being equal to or greater than ½ of a thickness of the piezoelectric layer.

What is claimed is: 
     
       1. An acoustic wave resonator comprising:
 a support substrate; 
 a piezoelectric layer that is disposed on the support substrate and is a rotated Y-cut X-propagation lithium tantalate of which a cut angle is within a range of 70° or greater and 90° or less; and 
 a pair of comb-shaped electrodes disposed on the piezoelectric layer, each of the comb-shaped electrodes including a plurality of electrode fingers, an average pitch of the electrode fingers of one of the comb-shaped electrodes being equal to or greater than ½ of a thickness of the piezoelectric layer. 
 
     
     
       2. The acoustic wave resonator according to  claim 1 , further comprising an insulating layer that is interposed between the support substrate and the piezoelectric layer, contains silicon oxide, and has a temperature coefficient of an elastic constant that is opposite in sign to a temperature coefficient of an elastic constant of the piezoelectric layer,
 wherein the average pitch of the electrode fingers of one of the comb-shaped electrodes is equal to or greater than ½ of a distance between an upper surface of the piezoelectric layer and a lower surface of the insulating layer. 
 
     
     
       3. The acoustic wave resonator according to  claim 2 ,
 wherein the thickness of the insulating layer is equal to or greater than 0.1 times the average pitch of the electrode fingers of the one of the comb-shaped electrodes and equal to or less than 0.7 times the average pitch of the electrode fingers of the one of the comb-shaped electrodes, 
 wherein a thickness of the piezoelectric layer is equal to or greater than 0.2 times the average pitch of the electrode fingers of the one of the comb-shaped electrodes and equal to or less than 0.6 times the average pitch of the electrode fingers of the one of the comb-shaped electrodes. 
 
     
     
       4. The acoustic wave resonator according to  claim 2 ,
 wherein the thickness of the insulating layer is equal to or greater than 0.3 times the average pitch of the electrode fingers of the one of the comb-shaped electrodes and equal to or less than 0.7 times the average pitch of the electrode fingers of the one of the comb-shaped electrodes, 
 wherein a thickness of the piezoelectric layer is equal to or greater than 0.3 times the average pitch of the electrode fingers of the one of the comb-shaped electrodes and equal to or less than 0.5 times the average pitch of the electrode fingers of the one of the comb-shaped electrodes. 
 
     
     
       5. The acoustic wave resonator according to  claim 2 , wherein the insulating layer is a silicon dioxide layer. 
     
     
       6. The acoustic wave resonator according to  claim 1 , wherein the average pitch of the electrode fingers of the one of the comb-shaped electrodes is a value calculated by dividing a length of the one of the comb-shaped electrodes in a direction in which the electrode fingers are arranged by the number of the electrode fingers. 
     
     
       7. The acoustic wave resonator according to  claim 1 , wherein the support substrate is a sapphire substrate, an alumina substrate, a silicon substrate, a spinel substrate, a crystal substrate, a quartz substrate, or a silicon carbide substrate. 
     
     
       8. A filter comprising:
 the acoustic wave resonator according to  claim 1 . 
 
     
     
       9. A multiplexer comprising:
 the filter according to  claim 8 .